Since the 1970s, the South Korean government has been redeveloping blighted residential environments and adopting large-scale redevelopment policies to solve urban housing-related problems. However, it is difficult to designate areas for redevelopment and identify areas where redevelopment is currently unfeasible. This study establishes a framework to support decision-making in a selection of housing renewal districts. The proposed Residential Environment Maintenance Index (REMI) overcomes the limitations of existing indicators, which are often biased toward physical requirements. Using this, we rationalize the designation of maintenance areas by considering both physical and social requirements and outline the renewal district designation procedure. To derive REMI, we used an analytic hierarchy process analysis and estimated the index's reliability by clarifying the relative importance and priority of the indicators based on surveys of 300 subject matter experts. We analyzed various simulations by applying REMI at sites where maintenance is currently planned or discharged in Seoul. These reveal that the total number of urban renewal projects can be adjusted by adjusting the number of renewal district designations through the proposed REMI according to the economic situation. The results have implications for understanding REMI's possible application and flexible management at the administrative level to pursue long-term sustainable development.Sustainability 2019, 11, 5876 2 of 20 of housing types [7], deletion of existing urban tissue [8], low resettlement rate of indigenous people [5], and destruction of communities' unique characteristics [9]. To systematically and efficiently manage and maintain the residential areas that have deteriorated and need improving, various projects have been implemented under the government's initiative [7]. Accordingly, the "Act on the Improvement of Urban Areas and Residential Environments" (hereinafter, the IUARE Act) [10], which encompasses a systematic management plan for improving deteriorated residential areas, was enforced in 2002. The IUARE Act contributes to the improvement of urban environments and the quality of residential life by integrating housing development projects and housing reconstruction projects, regenerating declining infrastructure, and renewing deteriorated housing infrastructure. The IUARE Act details four steps to implement an urban renewal project (Figure 1). The first step is to develop a master plan for a housing redevelopment or reconstruction project. In the second step, the maintenance area is designated. Maintenance of an area must form a part of any urban renewal project. In other words, areas that are intended to be redeveloped to improve the residential environment should first be designated as maintenance areas. In the second step, approval is obtained to form the Promotion Committee, and the establishment of a renewal association is authorized with the consent of at least 75% of the landowners. The third step involves issuing an urban renew...